1 package (2 1/2 teaspoons) active dry yeast, or 2/3 ounce fresh cake yeast
2/3 cup milk, room temperature
3 1/2 cups unbleached all-purpose flour, plus more for baking sheet
1/3 cups sugar
2 teaspoons coarse salt
3 large eggs
7 tablespoons unsalted butter, room temperature, cut into 6 to 8 pieces
Canola oil, for frying
Optional Ingredients for dusting: Cinnamon & Sugar or Confectioner’s Sugar
1. In the bowl of an electric mixer fitted with the dough hook attachment, stir together yeast and milk; let stand until yeast is dissolved, about 1 minute. Add flour, 1/3 cup sugar, salt, and eggs; mix on low speed until dough comes together, about 1 minute. Continue mixing on low 2 to 3 minutes more. Add butter, a few pieces at a time, mixing after each addition and until butter is fully incorporated and dough is soft, 5 to 6 minutes.
2. Remove dough from bowl and wrap tightly with plastic wrap. Refrigerate at least 6 hours and up to 15 hours.
3. Lightly flour a baking sheet; set aside. On a well-floured work surface, roll out dough into 12-inch square about 1/2 inch thick. Using a 3 1/2-to-4-inch round biscuit cutter, cut out 9 doughnuts. Transfer to prepared baking sheet and cover with plastic wrap; let stand in a warm spot until they’ve doubled in height and feel poufy and pillowy, 2 to 3 hours.
4. Fill a large heavy-bottomed saucepan with oil to a depth of 3 inches; heat over medium-high heat until it reaches 350 degrees on a deep-fry thermometer. Working in batches, place doughnuts in the hot oil, taking care not to crowd them. Fry until golden brown on one side, 2 to 3 minutes; turn and continue frying on remaining side until golden, 2 to 3 minutes more. Using a slotted spoon, transfer doughnuts to a paper towel-lined baking sheet until cool enough to handle.
5. Toss donuts in your favorite coatings: cinnamon and sugar or just plain confectioner’s sugar. If you want to dress it up, dip them in chocolate ganache.